Lu Gongxuan

Adsorption of chromium(VI) ions on to TiO2 from aqueous solution

The study of the adsorption of the CrVI ion on to TiO2 not only provides information on the removal of heavy metal ions from polluted aqueous solutions; but is also useful for further investigation of the photocatalytic decontamination of the CrVI ion or of CrVI–organic species which co-exist as pollutants with TiO2 when the latter is used as a stable and highly efficient photocatalyst. It has been found that dark adsorption of the CrVI ion on to TiO2 is mainly dependent on the acidity of the system and the initial concentration of the CrVI ion. As the pH of the system increases, so the extent of adsorption of the CrVI ion decreases. The greatest adsorption was obtained with an initial CrVI ion concentration of ca. 300 μmol/l. The presence of phosphate or acetate ions in the system dramatically decreases the adsorption efficiency of the CrVI ion. In contrast, the addition of formic acid leads to a limited increase in the extent of CrVI ion adsorption. Other organic ions and organic compounds examined showed no interference in CrVI ion adsorption. FT-IR spectroscopic methods were used for the characterization of CrVI ion adsorption on to TiO2.

Alteration of the catalytic properties of anatase by shock-wave loading

Abstract The alteration of the properties of anatase by exposure to a shock wave was investigated by X-ray diffraction spectroscopy (XRD), electron spin resonance (ESR), inductively coupled plasma atomic emission spectroscopy (ICP) and transmission electron microscopy (TEM) methods. Broadening of XRD profiles was observed after shock-wave loading. The isotropic ESR signal for g = 2.000, ascribed to F-centers, increased 2.5 times after that treatment. In contrast, the signal strength for g = 1.993 decreased to half of the original. Shocked anatase TiO 2 exhibited 1.5 times higher photoactivity for hydrogen evolution than that of unshocked material. A possible mechanism of shock-wave alteration is proposed.

Preparation of CdS/Graphene Composites and Photocatalytic Hydrogen Generation from Water under Visible Light Irradiation

CdS/graphene composite photocatalysts were prepared by photocatalytically reducing graphene oxide with CdS nanoparticles in an aqueous ethanol solution. The structure and photoelectrical properties of the resulted materials were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and transient photocurrent measurements. The photocatalytic activities of the CdS/graphene composites for hydrogen evolution were evaluated under visible light irradiation (λ≥420 nm). The results show that the graphene oxide can be efficiently reduced by the photogenerated electrons of CdS and thus CdS/graphene composite is formed and it shows strong interactions between CdS and graphene. Compared with CdS, the enhanced photocurrent generation and photocatalytic activity toward hydrogen evolution for the CdS/ graphene composite photocatalysts could be attributed to the ability of graphene to capture and transport electrons, and to promote charge separation.